Combine harvesters used today for harvesting grain crops in most parts of the world are designed to harvest a number of different seeds and cereal grains. They harvest grass seeds, canola, soybeans, corn, barley, oats, rice, wheat and many more crops. These crops are normally harvested by severing a substantial portion of the plant that extends upward from the ground and root system. The severed plant material is then gathered and conveyed into a combine harvester for threshing, separation of grain and cleaning of grain.
The seeds or grain kernels of many crops are found at the very top portion of the plant in heads supported by stalks. Because there is some variation in the heights of the heads from one stalk to another it is necessary to sever a substantial portion of the stalks to insure that substantially all the heads are recovered and that few are lost. Severing heads with a substantial portion of the stalks attached substantially increases the volume of material that is delivered to the threshing, separating and cleaning mechanisms.
The capacity of a combine harvester is generally limited by two primary factors. One limiting factor is the speed at which crop material can be severed and gathered. Another limiting factor is the rate at which the gathered crop material can be threshed and the grain can be separated and cleaned. For most harvesting systems the rate at which crops can be harvested is limited by the machines ability to thresh, separate and clean the grain. The ability to thresh, separate and clean is reduced in heavy crop conditions when handling large quantities of straw. National Research Development Corporation of England has developed stripper headers, shown in U. S. Pat. No. 5,111,645 to Klinner. The Klinner stripper header strips heads and grain from stalks or straw and conveys the stripped heads and grain to a threshing mechanism. The stalks or straw are for the most part left attached to their roots and standing upright. Only the heads and grain are gathered and fed to the threshing mechanism. The Klinner stripper header eliminates the crop cutting device and substantially reduces the quantity of straw or stalks that is conveyed to the threshing mechanism. Reducing the quantity of straw or stalks passing into the threshing mechanism substantially reduces the time required to harvest, thresh, separate and clean a crop. A stripper header thereby reduces the time required to harvest a crop. The end result is that a crop can be harvested in less time or the crop can be harvested with fewer machines.
The stripper header works well in many crops and in a wide range of crop conditions. However, grain losses can occur. The stripping rotor may fail to completely strip the heads and grain or the heads and grain that are detached by the stripping rotor may be lost. The stripper header may also convey stripped heads and grain unevenly to the threshing mechanism. Uneven feed of heads and grain to the threshing mechanism can reduce the efficiency of the threshing system and result in grain loss. In extreme conditions uneven feeding and bridging of material may cause plugging in the stripper header, or threshing components.